American Science and Engineering (AS and E) proposes to utilize its patented X-ray detection technique and its extensive patented and proprietary digital data-handling techniques to build an X-ray mammographic imaging system which will produce diagnostic images that match or exceed the information content of existing techniques with a radiation burden of approximately 30 mR skin entrance exposure. The system will be capable of imaging 10 lp/mm. over the entire breast, visualizing a calcification which is 0.2 mm. in diameter. In addition, the system will be able to differentiate smaller density fluctuations than can any X-ray system which currently exists. A 2 mm. tissue tumor imbedded in a 6 cm.-thick breast will be imaged at a signal-to-noise ratio of 19 to 1. AS and E has succeeded to producing a single high spatial resolution, high efficiency detector of limited length. The Phase I research will be to combine three of these modular elements with existing data acquisition and display systems to produce images over a larger field. This will demonstrate the ability to digitally align modules and obtain high quality images over distances exceeding one module length. However limitations in data acquisition speed will prevent imaging times less than 30 seconds. Phase II research will combine 10 modular detectors with high speed data acquisition devices and specially designed mechanical devices to provide a prototype imaging device for phantom evaluation and limited human volunteer field testing. The expected successful conclusion of this testing will lead directly to the establishment of breast cancer screening centers throughout the country.